This invention relates to a printing apparatus, a facsimile apparatus and/or an image processing apparatus using the printing apparatus and, more particularly to a printer which performs printing by scanning its printhead plural times, a facsimile apparatus and/or an image processing apparatus using the printing apparatus.
Conventional printers and facsimile apparatuses using a printer do not comprise a function for switching normal printing to multipath printing (printing by scanning a printhead plural times at the same scan area) or vice versa, in the middle of printing, in the middle of printing for one page, or in the middle of communication.
Further, there has been no device that automatically switches normal printing to multipath printing or vice versa in accordance with set operation mode, the type of output image, transfer speed of print data or time for decoding.
Furthermore, there has been no device that inputs from an operation panel the number of scanning operations of multipath printing.
Regarding multipath printing, Japanese Patent Application Laid-Open No. 60-107975 proposes a method for this type of printing. Further, European Patent Application No. 632405 A2 and Japanese Patent Application Laid-Open No. 7-52465 propose advanced multipath printing. European Patent Application No. 632405 A2 proposes print control to switch over of multipath printing to normal printing or vice versa.
However, in a serial printer using the conventional multipath printing method, printed results have stripe-like undesirable density unevenness at boundaries between scanned print areas, or different printing characteristic of each dot printed by the printhead becomes apparent to human eyes for each scan period, which causes degradation of image equality. Accordingly, a print range printed by one scanning is divided into a plurality of print areas, and each print area is scanned plural times, then the nozzles of the printhead are selected at random at each scanning, thus reducing the conspicuous striped density unevenness at boundaries between scanned print areas and density unevenness due to the characteristics of the respective nozzles, to prevent the degradation of image quality.
Next, the conventional multipath printing method will be briefly described.
FIG. 9 is a perspective view showing the structure of an ink-jet printer IJRA according to a typical conventional ink-jet printing method. In FIG. 9, a head carriage (HC) 5014 is engaged with a spiral groove 5004 of a lead screw 5005 which rotates via drive force transmission gears 5009 to 5011 interlocking with forward/reverse rotation of a carriage (CR) motor 5013. The head carriage 5014 reciprocally moves in directions represented by arrows a and b. The carriage 5014 has an ink-jet cartridge (IJC) 400. A paper holding plate 5002 presses a print sheet P against a platen 5000 along the moving direction of the carriage. Photosensors 5007 and 5008 are home position detectors for confirming the existence of lever 5006 of the carriage in this area and changing the rotational direction of the motor 5013. A support member 5016 supports a cap member 5022 for capping the front surface of the printhead (IJH) 5012. A suction member 5015 performs suction-restoration of the printhead via a cap inner opening 5023 by sucking the inside of the cap member 5022. Member 5019 allows a cleaning blade 5017 to move. A main body support plate 5018 supports the member 5019 and the cleaning blade 5017. A lever 5021 is for starting the sucking operation. It moves with a cam 5020 engaged with the carriage. The ink-jet cartridge 400 constituted with an ink tank (IT) 5001 and the ink-jet head (IJC) 5012 is supported by the carriage home-position detectors, a guide rail 5003 and an electrical connection point 5024, and is attached/detached to/from the head carriage 5014. A paper feed (PF) motor 5025 feeds the print sheet P.
FIG. 10 shows an example of a print model of two-scan multipath printing (two-path printing). For the purpose of simple explanation, a printhead employed here has eight ink nozzles for discharging ink. The nozzles are divided into two nozzle groups for four dots (four nozzles), and printing at one print area is made by respectively assigned nozzles. As a multimask pattern, a checker pattern for complementary ink-discharging is used, thus obtains constant printing density.
FIG. 11 shows an example of a print model of four-path printing. In this printing, the printhead nozzles are separated into four groups, and printing in one print area is made by four different nozzle groups. In FIG. 11, to perform printing at a print area 1, in a first scan, a mask pattern A1 is used; in a second scan, a mask pattern Bl is used; in a third scan, a mask pattern C1; and in a fourth scan, a mask pattern D1 is used. By the four mask patterns A1, B1, C1 and D1, printing in the print area 1 is 100% completed.
FIG. 12 is a block diagram showing the construction of a control circuit for controlling print data and multimask patterns. In FIG. 12, reference numeral 101 denotes a data register, connected to a memory data bus, for reading print data stored in a print buffer 130 in a memory and storing the read print data; 102, a parallel/serial converter for converting the print data in the data register 101 into serial data; 103, an AND gate for masking the serial data; 104, a counter for management of the number of data-transfer operations; 105, mask registers A to D, connected to a CPU 110, for storing mask patterns; 106, a selector for selecting a line position of a mask pattern in accordance with output from a column counter 111; and 107, a selector for management of digit positions.
In the control circuit, the print data is serial-transferred to the printhead in accordance with a print command signal from the CPU 110. That is, the print data stored in the print buffer 130 is temporarily stored in the data register 101, and converted by the parallel/serial converter 102 into serial data. Then, the serial data is masked by the AND gate 103, and transferred to the printhead. On the other hand, the transfer counter 104 counts the number of transfer-bits, and instructs the end of data transfer for one column.
The mask register 105 constituted with the four mask registers A, B, C and D holds mask patterns written by the CPU 110. The selector 107 selects mask pattern data corresponding to a line position based on the value of the transfer counter 104 as a selection signal. The mask pattern data selected by the selectors 106 and 107 is used for masking in the transfer data the AND gate 103.
However, in this conventional technique, assuming that the number of scan operations in multipath printing at one print area is n, print time is n times longer than normal printing. For the practical use, to perform printing such that density unevenness and stripes at boundaries between the print areas are inconspicuous, and to improve image quality, at least four scan operations are necessary. This results in print time four times longer than the normal printing.
Further, in the conventional printer, selection of normal printing/multipath printing is made by manual operation, and switch over of the print mode in the middle of printing or in the middle of printing for one page is not normally done. Furthermore, the selection of normal printing/multipath printing is not automatically performed in accordance with set mode of the printer or the type of print data. Accordingly, in a case where a part of an image to be printed or a part of an image received via communication is a halftone image in which boundaries between print areas will tend to be conspicuous, if the initial set mode is the normal print mode, the print mode is not switched to the multipath print mode. As a result, print image have conspicuous density unevenness and/or stripes at boundaries between print areas, thus the image quality is degraded.
On the other hand, if the initial set mode is the multipath print mode, even when print data is binary image data or very simple image data, where boundaries between print areas will be inconspicuous, the print time becomes long.